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After two weeks of prep, The Most Famous Christmas Tree in the World is ready to sparkle.

The switch will be flipped on the Rockefeller Center Christmas tree's 45,000 LED lights during a two-hour celebration Wednesday, a tradition dating back to 1933, the year the famed building opened.

"It's such an iconic event for New York and the whole country," said Bill Bracken, who is producing NBC's tree-lighting show for the fourth consecutive year. "We just try to present some of the biggest performers. Rod Stewart, Mariah Carey, Cee Lo Green, Trace Adkins, Tony Bennett … It’s a huge lineup this year."

Most of the nation will see an hour-long special at 8 p.m. hosted by Al Roker and Savannah Guthrie, featuring performances by the Rockettes and the Muppets. Some NBC stations, including NBC 4 New York and NBC Connecticut, will air a two-hour special beginning at 7 p.m.

Hundreds of thousands of people pack the streets surrounding the plaza for the tree lighting, Bracken said, with many watching the action on giant screens set up along side streets. Bracken says he strives to "capture the event for the people at home, so they get a sense of the scope of it."

The annual event was inspired by construction workers who erected a tree of their own in 1931, decorating it with cranberries, paper garland and tin cans, according to Daniel Okrent's "Great Fortune: The Epic of Rockefeller Center."

First televised in 1951 on NBC, which makes its home in the building, the tree lighting has grown to attract a quarter-million spectators and an audience of millions. With so many eyes on the tree, nothing is left to chance — organizers have backup generators on hand in case of a power outage.

This year's model, a Norway spruce from Morris County, N.J., about 50 miles west of Rockefeller Center, arrived on Nov. 14. The tree stands in the center of the plaza bound by 48th and 51st streets, and Fifth and Sixth avenues, looming 80 feet high, with a 50-foot waist and weighing 10 tons.

The trees are typically donated by people from the tri-state area and New England. The tallest of all time was 1999's 100-footer from Killingworth, Conn. And Rockefeller Center is always looking for next year's version, so if you've got a tree measuring at least 75 feet tall and 45 feet in diameter that you think has what it takes to adorn The Rock, you can submit your tree for consideration.

After Wednesday's tree lighting, the tree will be lighted every day from 5:30 a.m. to 11:30 p.m. until Jan. 7. After that, it will be put to good use: Since 2007, Rockefeller Center trees have been donated to Habitat for Humanity to be turned into lumber for affordable housing. Last year's tree was returned to Pennsylvania, where it was used to construct a pair of homes on Morse and Gratz streets in Philadelphia.